A. Technical Field
The present invention relates to hearing devices, and, more particularly, to miniature hearing devices that are deeply positioned in the ear canal for improved energy efficiency, sound fidelity, and inconspicuous extended wear.
B. Description of the Prior Art
Brief Description of Ear Canal Anatomy
The external acoustic meatus (ear canal) is generally narrow and contoured as shown in the coronal view in FIG. 1. The ear canal 10 is approximately 25 mm in length from the canal aperture 17 to the center of the tympanic membrane 18 (eardrum). The lateral part (away from the tympanic membrane) of the ear canal, a cartilaginous region 11, is relatively soft due to the underlying cartilaginous tissue. The cartilaginous region 11 of the ear canal 10 deforms and moves in response to the mandibular (jaw) motions, which occur during talking, yawning, eating, etc. The medial (towards the tympanic membrane) part, a bony region 13 proximal to the tympanic membrane, is rigid due to the underlying bony tissue. The skin 14 in the bony region 13 is thin (relative to the skin 16 in the cartilaginous region) and is more sensitive to touch or pressure. There is a characteristic bend 15 that roughly occurs at the bony-cartilaginous junction 19 (referred to herein as the bony junction), which separates the cartilaginous 11 and the bony 13 regions. The magnitude of this bend varies among individuals.
A cross-sectional view of the typical ear canal 10 (FIG. 2) reveals generally an oval shape and pointed inferiorly (lower side). The long diameter (DL) is along the vertical axis and the short diameter (DS) is along the horizontal axis. Canal dimensions vary significantly among individuals as shown below in the section titled Experiment.
Hair 5 and debris 4 in the ear canal are primarily present in the cartilaginous region 11. Physiologic debris includes cerumen (earwax), sweat, decayed hair, and oils produced by the various glands underneath the skin in the cartilaginous region. Non-physiologic debris consists primarily of environmental particles that enter the ear canal. Canal debris is naturally extruded to the outside of the ear by the process of lateral epithelial cell migration (see. e.g., Ballachanda, The Human ear Canal, singular Publishing, 1995, pp. 195). There is no cerumen production or hair in the bony part of the ear canal.
The ear canal 10 terminates medially with the tympanic membrane 18. Laterally and external to the ear canal is the concha cavity 2 and the auricle 3, both also cartilaginous. The junction between the concha cavity 2 and the cartilaginous part 11 of the ear canal at the aperture 17 is also defined by a characteristic bend 12 known as the first bend of the ear canal.
Several types of hearing losses affect millions of individuals. Hearing loss particularly occurs at higher frequencies (4000 Hz and above) and increasingly spreads to lower frequencies with age.
The Limitations of Conventional Canal Hearing Devices
Conventional hearing devices that fit in the ear of individuals generally fall into one of 4 categories as classified by the hearing aid industry: (1) Behind-The-Ear (BTE) type which is worn behind the ear and is attached to an ear mold which fits mostly in the concha; (2) In-The-Ear (ITE) type which fits largely in the auricle and concha cavity areas, extending minimally into the ear canal; (3) In-The-canal (ITC) type which fits largely in the concha cavity and extends into the ear canal (see Valente M., Strategies for Selecting and Verifying Hearing Aid Fittings, Thieme Medical Publishing. pp. 255-256, 1994), and; (4) Completely-In-the-Canal (CIC) type which fits completely within the ear canal past the aperture (see Chasin, M. CIC Handbook, Singular Publishing (xe2x80x9cChasinxe2x80x9d), p. 5, 1997).
The continuous trend for the miniaturization of hearing aids is fueled by the demand for invisible hearing products in order to alleviate the social stigma associating hearing loss with aging and disability. With continued improvements in miniaturization of hearing aid components, the battery has emerged as the largest single component in canal hearing devices (ITC and CIC devices are collectively referred to herein as canal devices or canal hearing devices). The conventional battery, button-cell type, remains predominantly used in virtually all hearing aid devices.
In addition to the cosmetic advantage of canal devices, there are actual acoustic benefits resulting from the deep placement of the device within the ear canal. These benefits include improved high frequency response, less distortion, reduction of feedback and improved telephone use (Chasin, pp. 10-11).
However, even with advances leading to the advent of canal devices, there remains a number of fundamental limitations associated with the underlying design and configurations of conventional canal device technology. These problems include: (a) frequent device handling, (b) oscillatory (acoustic) feedback, (c) custom manufacturing and impression taking, (d) energy inefficiency, (e) space inefficiency related to current battery designs, and (f) occlusion related problems. These limitations are discussed in more detail below.
(a) Frequent device handling: Conventional canal devices require frequent insertion and removal from the ear canal. Manufacturers often recommend daily removal for cleaning and maintenance of the CIC device (see, e.g., Users""s Instructions, SENSO CIC and Mini Canal, Widex Hearing Aid Co. February 97, pp. 11, 16; and General Information for Hearing aid Users, Siemens Hearing Instruments, Inc. March 98, p. 8). Daily removal of conventional CICs is also required for relieving the ear from the pressures of the device occluding the cartilaginous region. Furthermore, CIC hearing aid removal is also required in order to replace the conventional button-cell battery, typically lasting less than 2 weeks. The manual dexterity required to manipulate a canal device or replace a conventional battery, daily, poses a serious challenge to many hearing impaired persons who are elderly. These individuals typically suffer from arthritis, tremors, or other neurologic problems that limit their ability to frequently handle a miniature hearing aid.
(b) Oscillatory feedback occurs when leakage (arrows 32 and 32xe2x80x2 in FIG. 3) from sound output 30, typically from a receiver 21 (speaker), occur via a leakage path or a vent 23. The leakage (32xe2x80x2) reaches a microphone 22 of a canal hearing device 20 causing sustained oscillation. This oscillatory feedback is manifested by xe2x80x9cwhistlingxe2x80x9d or xe2x80x9csquealingxe2x80x9d and is not only annoying to hearing aid users but also interferes with their communication. Oscillatory feedback is typically alleviated by tightly occluding (sealing) the ear canal. However, due to imperfections in the custom manufacturing process (discussed below) or to the intentional venting incorporated within the hearing device (also discussed below) it is often difficult if not impossible to achieve the desired sealing effect, particularly for the severely impaired who require high levels of amplification. Oscillatory feedback typically occurs at high frequencies due to the presence of increased gain at these frequencies.
(c) Custom manufacturing and impression taking Conventional canal devices are custom made according to an impression taken from the ear of the individual. A canal device housing 25 (FIG. 3), known as shell, is typically custom fabricated according to an individual impression to accurately assume the shape of the individual ear canal. Customizing a conventional canal device is presumed required in order to minimize leakage gaps, which cause feedback, and also to improve the comfort of wear. Custom manufacturing is an imperfect process, time consuming and results in considerable cost overheads for the manufacturer and ultimately the hearing aid consumer (user). Furthermore, the impression taking process itself is often uncomfortable for the user.
(d) Energy inefficiency of conventional canal device is partially due to the distance or residual volume (6 in FIG. 3) between the receiver (speaker) 21 and the tympanic membrane 18. The further the receiver is from the tympanic membrane, the more air mass there is to vibrate; thus, more energy is required. However, due to concerns related to discomfort and difficulty of insertion, CIC products are typically tapered at their medial end 23 (Chasin, pp. 9-10) and relatively shallow in their placement (FIG. 3) in order to avoid substantial contact of the rigid enclosure with the bony portion of the ear canal.
(e) Space inefficiency related to current battery designs: Conventional canal devices employs a unitary enclosure 25 (shell) to protect the internal components within (battery 26, microphone 22, amplifier 24 and receiver 21 in FIG. 3). The shell 25, or a main housing, is a permanent component of the canal device thus is made durable with substantial thickness of about 0.5 to 0.7 mm. The battery, essentially the largest single component of a canal hearing device, also has its own protective housing typically made of nickel-plated iron. This double enclosure of the battery adds considerable dimensions to the overall size of the device and makes it difficult to negotiate its insertion into contoured ear canals. The shape of the conventional button-cell battery is also problematic in view of the ear canal being oval in cross-section (FIG. 2) and cylindrically elongated along the longitudinal axis. Button-cell batteries are circular in cross-section and have length (L) shorter than the diameter (D) of the cross-section as shown in FIG. 4. For example the standard button-cell batteries, models 5A and 10A employed in virtually all conventional CIC devices), have length (L) of about 2.15 and 3.6 mm, respectively, versus a diameter (D) of about 5.8 mm for both.
(f) Occlusion related problems are several and include:
(i) Discomfort, irritation and even pain may occur due to canal abrasion caused by frequent insertion and removal of a canal device. A removal strand 7 (FIG. 3) is generally provided with canal devices to assist the wearer in the daily removal process. Due to the resultant discomfort and abrasion, canal devices are frequently returned to the manufacture in order to improve the custom fit and comfort (e.g., Chasin, p. 44). xe2x80x9cThe long term effects of the hearing aid are generally known, and consist of atrophy of the skin and a gradual remodeling of the bony canal. Chronic pressure on the skin lining the ear canal causes a thinning of this layer, possibly with some loss of skin appendagesxe2x80x9d (Chasin, p. 58).
(ii) Moisture and cerumen produced in the cartilaginous ear canal cause damage to the ear canal and the hearing device when the canal is occluded by the hearing device. xe2x80x9cThe humidity in the occluded portion of the canal increases rapidly. This is worse during hot and humid weather, following exercisexe2x80x9d (Chasin, pp. 57-58). To reduce the damaging effects of canal moisture, it is often recommended to remove a CIC device from the ear canal daily to reduce the damaging effects of moisture in the canal. Occlusion by a canal hearing device also interferes with the natural lateral extrusion of cerumen. Cerumen impaction (the blockage of the ear canal by earwax) may also occur when cerumen, produced in the cartilaginous region, is pushed and accumulated deeper in the bony region of ear canal by the frequent insertion of a CIC hearing device (e.g., Chasin, p. 27, pp. 56-57).
(iii) The occlusion effect is a common acoustic problem caused by the occluding hearing device. It is manifested by the perception of a person""s xe2x80x9cself-soundsxe2x80x9d (talking, chewing, yawning, clothes rustling, etc) being loud and unnatural compared to the same sounds with the open (unoccluded) ear canal. The occlusion effect is primarily due to the low frequency components of self-sounds, as is experienced, for example, by plugging the ears with fingers while talking. The occlusion effect is generally related to sounds resonating within the ear canal when occluded by the hearing device. The occlusion effect is demonstrated in FIG. 3 when xe2x80x9cself-soundsxe2x80x9d 35, emanating from various anatomical structures around the ear (not shown), reach the ear canal 10. When the ear canal is occluded, a large portion of self-sounds 35 are directed towards the tympanic membrane 18 as shown by arrow 34. The magnitude of xe2x80x9cocclusion soundsxe2x80x9d 34 can be reduced by incorporating an xe2x80x9cocclusion-relief ventxe2x80x9d 23 across the canal device 20. The occlusion-relief vent 23 allows a portion of the xe2x80x9cocclusion soundsxe2x80x9d 35 to leak outside the ear canal as shown by arrow 35xe2x80x2.
The occlusion effect is inversely proportional to the residual volume 6 of air between the occluding hearing device and the tympanic membrane. Therefore, the occlusion effect is considerably alleviated by deeper placement of the device in the ear canal. However, deeper placement of conventional devices with rigid enclosures is often not possible for reasons including discomfort as described above. For many hearing aid users, the occlusion effect is not only annoying, but is often intolerable leading to discontinued use of the canal device.
The above limitations in conventional canal devices are highly interrelated. For example, when a canal device is worn in the ear canal, movements in the cartilaginous region xe2x80x9ccan lead to slit leaks that lead to feedback, discomfort, the occlusion effect, and xe2x80x98pushingxe2x80x99 of the aid from the earxe2x80x9d (Chasin, pp. 12-14). The relationship between these limitations is often paradoxically adverse. For example, occluding the ear canal tightly is desired on one hand to prevent feedback. However, tight occlusion leads to the occlusion effect described above. Attempting to alleviate the occlusion effect by a vent 23 provides an opportunistic pathway for feedback. For this reason alone, the vent 23 diameter is typically limited in CIC devices to about 0.6-0.8 mm (Chasin, pp. 27-28).
Review of State-of the-Art in Related Hearing Device Technology
Cirillo, E., in U.S. Pat. No. 4,830,139 discloses means for holding a speaker mold (16 in Cirillo""s FIG. 1) in the ear canal via a sealant made of flexible gelatinous water-soluble material. The mold is attached to a wire (18) extending to the outside of the ear canal, and therefore, the Cirillo device is presumably for hearing devices that are positioned outside the ear canal. Cirillo""s disclosure does not deal with devices that are completely positioned in the ear canal. Furthermore, since the sealant is water-soluble it can also be assumed that the sealant is suitable only for short-term use as it will deteriorate with moisture exposure (e.g., when taking a shower, swimming, etc.).
Sauer et al., in U.S. Pat. No. 5,654,530, disclose an insert associated with an ITE device (Sauer""s FIG. 1) or a BTE device (Sauer""s FIG. 2). The insert is a xe2x80x9csealing and mounting elementxe2x80x9d made of xe2x80x9csoft elastic material having slotted outer circumference divided into a plurality of fan-like circumferential segmentsxe2x80x9d. The sealing element is positioned at the lateral portion of the ear canal as shown in the figures. Sauer""s disclosure teaches an insert for ITEs and BTEs and is apparently not concerned with inconspicuous hearing devices that are deeply and completely inserted in the ear canal. The insert is obviously in the cartilaginous area, thus occluding the ear canal in the region of hair, and cerumen and sweat production. Clearly, long term use (without daily removal) will interfere in the natural production of physiologic debris.
Garcia et al., in U.S. Pat. No. 5,742,692 disclose a hearing device (10 in Garcia""s FIG. 1) attached to a flexible seal 30 which is fitted in the bony region of the ear canal. The device 10 comprises hearing aid components (i.e., microphone 12, receiver 15 and battery 16, etc., as shown by Garcia) which are contained within a single xe2x80x9cunitaryxe2x80x9d housing 20. The device 10 is not likely to fit deeply and comfortably in many small and contoured canals due to the space inefficiency associated with the unitary housing 20. In addition to the size disadvantage, the device 10 occludes the ear canal in the cartilaginous region as shown in Garcia""s FIG. 2.
Henneberger and Biermans in U.S. Pat. Nos. 4,680,799 and 4,937,876, respectively, also disclose hearing aid devices with conventional housings, which occlude the ear canal and comprise a unitary enclosure for microphone, battery and receiver components within.
Weiss et al. in U.S. Pat. Nos. 3,783,201 and 3,865,998 disclose an alternate hearing device configuration which fits partially in the ear canal (FIG. 1 in both Weiss et al patents) with a separate microphone 14 and receiver 18. The main housing, enclosing battery and amplifier, are designed for fitting in the concha area outside the ear canal as shown. The microphone 14 is positioned in the pinna completely outside the ear canal. The device is obviously not completely placed in the ear canal and thus visible.
Geib in U.S. Pat. No. 3,527,901 discloses a hearing device with housing made of soft resilient material, which encloses the entire body of the device. This approach eliminates conventional rigid enclosures thus presumably more comfortable to wear. However, the unitary enclosure does not provide any improvement in space efficiency. Furthermore, the hearing device was clearly not designed to fit entirely in the ear canal, Geib stating that xe2x80x9cthe hearing aid makes a much better fit within the concha and ear canal of the user thereby providing a more effective seal and reducing the problems of direct acoustic feedbackxe2x80x9d (col 2, lines 40-43 of Geib).
Hardt in U.S. Pat. No. 4,607,720 discloses a hearing device which is mass-producible with a soft sealing plug that is serially attached to the receiver. Although the invention solves the problem of custom manufacturing, the unitary enclosure (containing major hearing aid components: battery, microphone and receiver) is also space-inefficient for deep canal fittings.
Voroba et al in U.S. Pat. No. 4,870,688 also discloses a mass-producable hearing aid. The device comprises a solid shell core (20 in Voroba""s FIGS. 1 and 2) which is covered by a flexible covering 30 affixed to the exterior of the rigid core 20. Similarly, the rigid core represents a unitary enclosure for containing all major hearing aid components, and thus, considered space-inefficient for deep canal fittings.
McCarrel, et al, Martin, R, Geib, et al., and Adelman R., in U.S. Pat. Nos. 3,061,689, RE26,258, 3,414,685 and 5,390,254, respectively, disclose miniature hearing devices with a receiver portion flexibly separate from a main part. The receiver portion is insertable into the ear canal with the main part occupying the concha (McCarrel""s FIG. 2, Geib""s FIG. 10, Adelman""s FIG. 3B). This placement facilitates access to the device for insertion and removal. The main part in the above devices contains all the major components of a hearing device including the battery, amplifier and microphone, but excluding the receiver. Therefore, the main part is not space-efficient sufficiently to fit the ear past the aperture of the ear canal for most individuals. Furthermore, the cartilaginous part of the ear canal is substantially occluded or not exposed to the outer environment, thus requiring frequent removal of the device from the ear canal.
Shennib et al, in U.S. Pat. No. 5,701,348, disclose an articulated hearing device with flexibly connecting modules. xe2x80x9cThe main module 12 includes all of the typical components found in hearing devices, except for the receiver (lines 64-66, col 6).xe2x80x9d The main module includes a battery 16, a battery compartment 15, circuit 17 (amplifier) and microphone 14. Because if its articulated design and assorted soft acoustic seal 43, the invented hearing device can fit a variety of ear canals without resorting to custom manufacturing, thus can be mass-producible as disclosed. Although a CIC configuration is disclosed (see FIG. 23 in Shennib), the depth of insertion, particularly for small and contoured ear canals, is severely limited by the design of the main module 12 which contains within the power source (battery) along with other major components (e.g., the microphone). Furthermore, the device in any of its disclosed configurations, substantially occludes the ear canal in the cartilaginous region, and thus could interfere with hair and the natural production of physiologic debris. Therefore, the disclosed CIC device of the Shennib is not suitable for extended wear.
It is a principal objective of the present invention to provide a highly space-efficient hearing device, which is completely positioned in the ear canal.
A further objective is to provide a mass-producible design which does not require custom manufacture or individual ear canal impression.
A further objective is to provide a hearing device which does not occlude the cartilaginous part of the ear canal thus minimally interfering with hair and the natural production and extrusion of physiologic debris in the ear canal.
Yet another objective of particular importance is to provide a canal hearing device which is suitable for extended wear, so that it does not require daily removal from the ear canal.
Extended wear as used in this specification and appended claims is defined as continuous placement and use of the hearing device within the ear canal without need for removal for a relatively significant period of time, at least about one week.
The present invention provides a generic canal hearing device, which is positioned deeply and completely within the ear canal, and is particularly suited for extended wear. The canal device occludes the bony part of the ear canal for sealing within while extending laterally into the cartilaginous part in a non-occluded fashion. The canal device comprises a cylindrically elongated battery assembly having a generally oval cross-sectional perimeter with a sectional void for mating with a universal core assembly. The battery assembly comprises a thin enclosure with an outer surface directly exposed to the environment of the ear canal. The invention is characterized by the lack of a unitary rigid enclosure or rigid main housing, typically enclosing a battery along with other components as in prior art designs.
The battery assembly is removably connected to the universal core assembly. The battery assembly and a microphone section of the core assembly form a lateral section when attached for positioning comfortably in the cartilaginous part of the ear canal past the aperture thereof.
The lateral section is substantially cylindrical with oval cross-sectional perimeter and medial tapering at the bony-junction of the ear canal. The oval cross-sectional perimeter of the lateral section is smaller than that of the ear canal thus makes little or no contact with the walls of the ear canal when inserted therein. The lateral section is therefore positioned in the ear canal in a non-occluding fashion with minimal interference with hair and earwax production. The acoustic occlusion effect is also minimized by directing occlusion sounds away from the eardrum towards the outside of the ear canal.
The core assembly also comprises a receiver section flexibly connected to the microphone section. The receiver section is positioned in the bony part of the ear canal past the bony-junction. The receiver section contains a receiver, which delivers sound towards the eardrum within exceptional proximity for minimizing energy consumption and improving high frequency response. The receiver section is securely anchored in the bony part of the ear canal by a conforming sealing retainer concentrically positioned around (i.e., over) the receiver section. The flexible connection between the receiver section and lateral section facilitates the insertion and removal of the hearing device in the ear canal, particularly through the bony-junction area.
In the preferred embodiments of the invention the battery assembly is generically in available in an assortment of various shapes and sizes for selection of optimal fit and maximum energy capacity according to the individual ear being fitted. The battery assembly in the preferred embodiments is disposable and comprises protruding contacts for insertion into the microphone section thus providing electrical and mechanical connections to the core assembly of the hearing device. In another embodiment of the invention, the core assembly is disposable and incorporates the battery within it.
The hearing device of the invention is mass-producible and accommodates a variety of canal shapes and sizes without resorting to custom manufacturing or canal impressions.
The space and energy efficient design of the invention allows for a comfortable extended use within the ear canal without resorting to daily removal as commonly required by conventional canal devices. In the preferred embodiments, the invented device is remotely switched on/off by a remote control for optionally conserving the battery energy while the device remains in the ear canal during sleep or non-use.